Process for concentrating oxidized lead ores



Patented ar. 31, 1942 Joseph T. Terry, Rosemead, Calif.

No Drawing. Application May 1, 1940, Serial No. 332,773

9 Claims.

My invention relates to a method of securing froth flotation of lead ores of the oxidized types for the purpose oi concentrating the same, and

more particularly to lead ores containing finely comminuted gold and silver.

Lead ores of the oxidized types, such as sulfates, carbonates (anglesite and cerussite), cannot be successfully concentrated by the usual flotation processes applicable to sulfid ores.

I have discovered that if a soluble cyanide is added to oxidized lead ores after pulverizing and mixing with water, finely comminuted gold and silver will b dissolved and can be recovered by the well known cyanide process and, if the ore is then washed until substantially all of the soluble cyanide is removed, it may then be concentrated by flotation. Furthermore, the previously non-flotatable oxidized lead ores will now be readily floated. It is my opinion that the reason for this phenomena is that lead sulfate and lead carbonate are appreciably soluble and a sulfld film thereon less stable than a sulfld film created over a less soluble lead cyanide coating. By the treatment with the soluble cyanide, a surface reaction probably results, leaving a minute layer of lead cyanides which are exwill be apparent from I the following description 01 the preferred form of my invention.

' In carrying out my invention in the preferred manner, the ore containing finely comminuted tremely insoluble. When treated by theusual sulfldizing method for floating unoxidized ores,

the oxidized ores having the minute cyanide layer beneath a sulfldized layer readily float.

This invention is an" improvement upon that set forth in my Patent No. 2,196,233 issued April 9, 1940, in that in the process set forth in my prior patent a very substantial portion of the finely comminuted gold and silver are lost and remain in the tailings.

It is, therefore, an object of my invention to provide a treatment of oxidized lead ores whereby said ores may be concentrated by a froth flotation process.

Another object of my invention is to provide a treatment of oxidized lead ores containing finely comminuted gold and silver whereby the finely comminuted gold and silver may be recovered by the usual cyanide process and the oxidized lead ore then concentrated by a froth flotation process.

Another object of my. invention is to provide a'treatment of oxidized lead ores whereby the soluble cyanide added thereto can be in strong concentration without preventing froth flotation and still increase the yield of such froth flotation.

Other objects andadvantages of my process being usually suflicient.

gold and silver and lead sulfate is reduced to a pulp by conventional methods, as in a ball mill, with sodium cyanide in any suitable concentrate, two pounds of sodium cyanide per ton of water Any concentration of soluble cyanide greater than one pound per ton of water will retard flotation. In conjunction therewith, I may use a suitable amount of protective alkali, such as sodium carbonate, in order to maintain a pH of between 6 and 9.

The pulp is subject to agitation to dissolve the finely comminuted gold and silver.

The pulp is then filtered and washed with watar as much as possible within economic limits to remove the soluble cyanide and dissolved gold and silver and permit the ores to be floated and the dissolved gold and silver to be recovered from the cyanide by the usual cyanide treatment.

When the pulp is substantially cyanide free, it is remixed with water to which is added 2 to 5 pounds of sodium sulfide per ton of dry ore which, I believe, reacts with the minute layer of lead cyanide to convert it to a minute layer of film oi lead sulfide over and interlacing the cyanide coating. Additional potassium ethyl xanthate and one or more flotation promoting agents, such as 'pineoil or cresylic acid, are added and the pulp lows: The ore from the Tintic Standard Mine of Dividend, Utah, assays: gold 0.03 02.; silver 24.6

oz. and lead 9.0 .per cent. The lead is in the form of an oxidized ore, namely anglesite and cerussite and the silver as finely comminuted metallic particles.

500 grams of this ore were ground and the heavy particles recovered by gravity concentration. The sands werereground to pass a 150 mesh screen and mixed with 1 liter of water, mgs. of potassium ethyl xanthate and 1 gram of sodium cyanide. This mixture was agitated for 6 hours and then filtered and the filtrate retained. The filter cake was then washed substantially free of soluble cyanide and then repulped with water. 1 gr. of sodium sulfide, 0.2 gr. of sodium silicate, 100 mg. of potassiumethyl xanthate, 5 drops of pineoil and 5 drops of oresylic acid, were added. Froth flotation was then carried out giving a rougher concentrate and a rougher tailing. The rougher concentrate from this flotation were then refloated giving a finished concentrate, and a middling or cleaner tailing which, in milling practice, would be returned for retreatment.

The concentration of the ores thus accomplished was: Finished concentrate plus gravity concentrate:

Gold oz 0.04 Silver oz 100.8 Lead per cent 31.7

Middling:

Gold oz 0.04 Silver oz.. 15.4 Lead per cent 5.1

Rougher tailings:

Gold oz 0.02 Silver oz 2.6 Lead per cent-.. 0.5

From this test it is readily apparent that I have accomplished nearly a 95 per cent concentration.

While I have shown and described the preferred embodiments of my invention, I do not wish to be limited to any details herein except as defined in the appended claims.

I claim:

1. The process of concentrating natural oxidized lead ores comprising the formation of a pulp of an oxidized lead ore, treating with a soluble cyanide, washing to remove substantially all of said soluble cyanide but retaining a portion of said soluble cyanide to form a substantially insoluble coating of lead cyanide, and removing a concentrate by froth flotation.

2. The process of concentrating natural oxidized lead ores comprising the formation of a pulp of an oxidized lead ore, adding an alkali cyanide to said pulp, washing to remove substantially all of said alkali cyanide, but retaining a portion of said soluble cyanide to form a sub-. stantially insoluble coating of lead cyanide, and removing a concentrate by froth flotation.

3. The process of concentrating natural oxidized lead ores comprising the formation of a pulp of an oxidized lead ore, adding to said pulp a soluble cyanide, removing substantially all of said soluble cyanide but retaining a portion of said soluble cyanide to form a substantially insoluble-coating of lead cyanide, repulping said ore, adding a soluble sulfide, and removing a concentrate by froth flotation.

4. The process of concentrating natural oxidized lead ores by treating a lead ore of the oxidized type with a soluble cyanide, washing to remove substantially all of the soluble cyanide but retaining a portion of said soluble cyanide to form a substantially insoluble coating of lead cyanide, and securing a concentrate by froth flotation.

5. The process of concentrating naturaloxidized lead ores containing finely comminuted gold or silver comprising the formation of a pulp of an oxidized lead ore containing finely comminuted gold or silver, adding a soluble cyanide, washing to remove substantially all of the soluble cyanide containing the dissolved gold or silver whereby said gold or silver may be recovered by the usual cyanide process but retaining a portion of said soluble cyanide to form a substantially insoluble coating of lead cyanide, repulping said ore and removing a concentrate by froth flotation.

6. The process of concentrating natural oxidized lead ores containing finely comminuted gold or silver comprising the formation of a pulp of an oxidized lead ore containing finely comminuted gold or silver, adding a soluble cyanide, removing substantially all of said soluble cyanide whereby the gold or silver dissolved therein may be recovered by the usual cyanide process but retaining a portion of said soluble cyanide to form a substantially insoluble coating of lead cyanide, repulping said ore and adding a soluble sulfide and a flotation promoting agent, and recovering aconcentrate by froth flotation.

7. The process of concentrating natural oxidized lead ores containing finely comminuted gold or silver comprising the formation of pulp of an oxidized lead ore containing finely comminuted gold or silver, adding an alkali cyanide, removing substantially all of said alkali cyanide, whereby the gold or silver dissolved therein may be recovered by the usual process but retaining a portion of said soluble cyanide to form a substantially insoluble coating of lead cyanide, repulping said ore, and recovering a concentrate by froth flotation.

8. The process of concentrating natural oxidized lead ores containing finely comminuted gold or silver comprising the formation of a pulp of an oxidized lead ore containing finely comminuted gold or silver, adding an alkali cyanide, removing substantially all of said alkali cyanide, whereby the gold or silver dissolved therein may be recovered by the usual cyanide process but retaining a portion of said soluble cyanide to form a substantially insoluble coating of lead cyanide, repulping said ore, and adding a soluble sulfide and a flotation promoting agent, and recovering a concentrate by froth flotation.

9. The process of concentrating natural oxidized lead ores containing finely comminuted gold or silver comprising the formation of a pulp of an oxidized lead ore containing finely comminuted gold or silver, adding a sodium cyanide, removing substantially all of said sodium cyanide, whereby the gold or silver dissolved therein may be recovered by the usual cyanide process but retaining a portion of said soluble cyanide to form a substantially insoluble coating of lead cyanide, repulping said ore, and adding sodium sulfide, potassium ethyl xanthate and pineoil, and recovering a concentrate by froth flotation.

JOSEPH T. TERRY. 

